Anion Absorption Research Articles

Modulating Interfacial Solvation via Ion Dipole Interactions for Low-Temperature and High-Voltage Lithium Batteries.

Extending the stability of ether solvents is pivotal for developing low-temperature and high-voltage lithium batteries. Herein, we elucidate the oxidation behavior of tetrahydrofuran with ternary BF4-, PF6- and difluoro(oxalato)borate anions and the evolution of interfacial solvation environment. Combined in-situ analyses and computations illustrate that the ion dipole interactions and the subsequent formation of ether-Li+-anion complexes in electrolyte rearrange the oxidation order of solvated species, which enhances the electrochemical stability of ether solvent. Furthermore, preferential absorption of anions on the surface of high-voltage cathode favors the formation of a solvent-deficient electric double layer and an anti-oxidation cathode electrolyte interphase, inhibiting the decomposition of tetrahydrofuran. Remarkably, the formulated electrolyte based on ternary anion and tetrahydrofuran solvent endows the LiNi0.8Co0.1Mn0.1O2 cathode with considerable rate capability of 5.0 C and high capacity retention of 93.12% after 200 cycles. At a charging voltage of 4.5 V, the Li||LiNi0.8Co0.1Mn0.1O2 cells deliver Coulombic efficiency above 99% at both 25 and -30 °C.

Modulating Interfacial Solvation via Ion Dipole Interactions for Low‐Temperature and High‐Voltage Lithium Batteries

Extending the stability of ether solvents is pivotal for developing low‐temperature and high‐voltage lithium batteries. Herein, we elucidate the oxidation behavior of tetrahydrofuran with ternary BF4‐, PF6‐ and difluoro(oxalato)borate anions and the evolution of interfacial solvation environment. Combined in‐situ analyses and computations illustrate that the ion dipole interactions and the subsequent formation of ether‐Li+‐anion complexes in electrolyte rearrange the oxidation order of solvated species, which enhances the electrochemical stability of ether solvent. Furthermore, preferential absorption of anions on the surface of high‐voltage cathode favors the formation of a solvent‐deficient electric double layer and an anti‐oxidation cathode electrolyte interphase, inhibiting the decomposition of tetrahydrofuran. Remarkably, the formulated electrolyte based on ternary anion and tetrahydrofuran solvent endows the LiNi0.8Co0.1Mn0.1O2 cathode with considerable rate capability of 5.0 C and high capacity retention of 93.12% after 200 cycles. At a charging voltage of 4.5 V, the Li||LiNi0.8Co0.1Mn0.1O2 cells deliver Coulombic efficiency above 99% at both 25 and ‐30 °C.

The Relevance of Phytate for the Treatment of Chronic Kidney Disease.

Diets high in plant-based foods are commonly recommended for people with chronic kidney disease (CKD). One putative advantage of these diets is reduced intestinal phosphate absorption. This effect has been ascribed to phytic acid (myoinositol hexaphosphoric acid) and its anion, phytate, that are present in many plant foods, particularly in the seeds, nuts, grains and fruits of plants. This paper reviews the structure and many actions of phytate with particular reference to its potential effects on people with CKD. Phytate binds avidly to and can reduce gastrointestinal absorption of the phosphate anion and many macrominerals and trace elements including iron, zinc, calcium and magnesium. This has led some opinion leaders to label phytate as an "anti-nutrient." The human intestine lacks phytase; hence, phytate is essentially not degraded in the small intestine. A small amount of phytate is absorbed from the small intestine, although phytate bound to phosphate is poorly absorbed. Clinical trials in maintenance hemodialysis patients indicate that intravenously administered phytate may decrease hydroxyapatite formation, vascular calcification and calciphylaxis. Orally administered phytate or in vitro studies indicate that phytate may also reduce osteoporosis, urinary calcium calculi formation and dental plaque formation. Phytate appears to have anti-inflammatory and antioxidant effects, at least partly due to its ability to chelate iron. Other potential therapeutic roles for phytate, not definitively established, include suppression of cancer formation, reduction in cognitive decline that occurs with aging, and amelioration of certain neurodegenerative diseases and several gastrointestinal and metabolic disorders. These latter potential benefits of phytate are supported by cell or animal research or observational studies in humans. Many of the above disorders are particularly common in CKD patients. Definitive clinical trials to identify potential therapeutic benefits of phytate in CKD patients are clearly warranted.

Multi-molar absorption of CO2 by a novel dual-functionalized ionic liquid solution: Experimental and DFT mechanistic study

Viscosity and absorption capacity are the main indexes to evaluate functionalized ionic liquids. Based on the precise design strategy of both anion and cation absorption, a dual-functionalized protic IL diethylenetriamine methylurea ([DETAH][MEUR]) for trapping CO2 was successfully synthesized. The absorption and regeneration properties of the ILs solution were tested, and the changes in the physical properties of ILs before and after CO2 absorption were compared. The experimental results showed that the [DETAH][MEUR] solution had relatively low viscosity, excellent absorption property with 2.05 mol CO2/mol IL at 40 °C and 0.5 mol/L concentration, and its regeneration efficiencies still kept above 90.09 % after five cycles. In addition, the mechanism of the absorption reaction was explored by combining Fourier transform infrared (FT-IR) spectroscopy, carbon nuclear magnetic resonance (13C NMR) spectroscopy, and density functional theory (DFT) calculation methods. It shows that in [DETAH][MEUR] solution, the N atom losing proton (-NH) in the anion is the main absorption site, and the primary amine (-NH2) in the protonated cation [DETAH]+ of secondary amine is used as an auxiliary cooperative trapping CO2. Hopefully, this work can provide a new way for the research and development of green CO2 absorbents.

INFLUENCE OF DINITROSALICYLIC ACID ON THE PROTECTIVE SYSTEM OF COTTON SEEDLINGS (Gossypium hirsutum L.)

Cotton growing, being an important agro-industrial object, is being improved through the introduction of new mechanisms to increase resistance to various external stress factors. Taking into account the previously studied phytohormones, the purpose of our study was to identify the effect of the salicylic acid derivative, dinitrosalicylic acid (DNSA), on the biochemical processes in the common cotton AP-317 genotype. It was established that low concentrations of DNSA-0.01 mM decreased production of NO radical, catalase and PPO activity, as well as absorption of phosphorus-anions from the nutrient medium, while higher doses of them has led to the stimulation of NO radical production, increased peroxidase activity, stabilized absorption of phosphorus anions. It was also found that at low concentrations of DNSA took place slightly activation of SOD activity, but not at relatively high concentration of DNSA. Electron paramagnetic resonance analysis of the root and leaf tissue of the plant showed an increase in the concentration of magnesium and iron ions when exposed to DNSA. It was also found that DNSA increased the concentration of lipid peroxide radicals at 0.1 mM in both tissues.

Accumulative Charge Separation in a Modular Quaterpyridine Bridging Ligand Platform and Multielectron Transfer Photocatalysis of π-Linked Dinuclear Ir(III)–Re(I) Complex for CO2 Reduction

Four sterically distorted quaterpyridyl (qpy) ligand-bridged Ir(III)-Re(I) heterometallic complexes (Ir-qpymm-Re, Ir-qpymp-Re, Ir-qpypm-Re, and Ir-qpypp-Re), in which the position of the coupling pyridine unit of the two 2,2'-bipyridine ligands was varied (meta (m)- or para (p)-position), pypyx-pyxpy (x = m and m, qpymm; x = m and p, qpymp; x = p and m, qpypm; x = p and p, qpypp), were prepared, along with the fully π-conjugated Ir(III)-[π linker]-Re(I) complexes (π linker = 2,2'-bipyrimidine (bpm), Ir-bpm-Re; π linker = 2,5-di(pyridin-2-yl)pyrazine (dpp), Ir-dpp-Re) to elucidate the electron mediating and accumulative charge separation properties of the bridging π-linker in a bimetallic system (photosensitizer-π linker-catalytic center). From the photophysical and electrochemical studies, it was found that the quaterpyridyl (qpy) bridging ligand (BL), in which the two planar Ir/Re metalated bipyridine (bpy) ligands were connected but slightly canted relative to each other, linking the heteroleptic Ir(III) photosensitizer, [(piqC^N)2IrIII(bpy)]+, and catalytic Re(I) complex, (bpy)ReI(CO)3Cl, minimized the energy lowering of the qpy BL, which hampers the forward photoinduced electron transfer (PET) process from [(piqC^N)2IrIII(N^N)]+ to (N^N)ReI(CO)3Cl (Ered1 = -(0.85-0.93) V and Ered2 = -(1.15-1.30) V vs SCE). This result contrasts with the fully π-delocalized bimetallic systems (Ir-bpm-Re and Ir-dpp-Re) that show a significant energy reduction due to the considerable π-extension and deshielding effect caused by the neighboring Lewis acidic metals (Ir and Re) on the electrochemical scale (Ered1 = -0.37 V and Ered2 = -1.02 and -0.99 V vs SCE). Based on a series of anion absorption studies and spectroelectrochemical (SEC) analyses, all Ir(III)-BL-Re(I) bimetallic complexes were found to exist as dianionic form (Ir(III)-[BL]2--Re(I)) after a fast reductive-quenching process in the presence of excess electron donor. In the photolysis experiment, the four Ir-qpy-Re complexes displayed the reasonable photochemical CO2-to-CO conversion activities (TON of 366-588 for 19 h) owing to the moderated electronic coupling between two functional Ir(III) and Re(I) centers through the slightly distorted qpy ligand, whereas Ir-bpm-Re and Ir-dpp-Re displayed negligible performances as a result of the strong electronic coupling via π-conjugation between the two functional components resulting in the energetic constraints for PET and an unwanted side reactions competing with the forward processes. These results confirm that the qpy unit can be utilized as an efficient BL platform in π-linked bimetallic systems.

GhCLC5/16 genes participate in the regulation of Cl−-salinity tolerance in seedlings of different upland cotton cultivars

For plants or crops exposed to salinity stress, chloride channels (CLCs) play crucial functions in the regulation of anion (such as Cl− and NO3−) absorption, transport and distribution or anion homeostasis. In this study, how the physiological functions and molecular mechanisms of GhCLC5/16 genes affect Cl− -salinity tolerance in two upland cotton cultivars (the salt-tolerant cv. Lu7619 and the salt-sensitive cv. Xin51) was investigated using transformations of the yeast Δgef1 mutant, soybean hairy-root, Arabidopsis atclc-b mutant, and virus-induced gene silencing (VIGS) cotton plants. The results showed that, the target GhCLC5/16 genes, with the higher NaCl-induced upregulation of expression in the roots of Lu7619 plants, could complement the Cl−-sensitive phenotype of the yeast Δgef1 mutant. Under NaCl stress, compared to empty vector (EV) plants, GhCLC5/16-overexpressed soybean hairy-root composite plants (hrGhCLC5/16-OE) displayed enhanced NaCl tolerance with superior growth, lower relative electrolytic leakage (REL) values and malondialdehyde (MDA) contents in roots and leaves. Compared to the atclc-b mutant, atclc-b-GhCLC5 and atclc-b-GhCLC16 Arabidopsis seedlings displayed improved NaCl tolerance with less reduced root length, higher leaf chlorophyll content, lower shoot MDA content and REL values. GhCLC5/16-VIGS cotton plants displayed mitigated salt damage with significantly higher plant height and fresh weight (FW) than that of EV plants. The enhanced NaCl tolerance or mitigated salt damage of these plants, even with the salt-tolerant cv. Lu7619 (characterized by high GhCLC5/16 expression in the roots, whole plants, or GhCLC5/16-silencing in the leaves), occurs because the plants can accumulate more Cl− in the roots under NaCl stress, reduce the transport and accumulation of Cl− to shoots (especially the leaves), simultaneously enhance the NO3− content in the shoots/leaves, and thus significantly decrease the Cl−/NO3− ratio in the shoots/leaves. Therefore, GhCLC5/16 genes may be crucial members of the GhCLC family that contribute to the varied tolerance to Cl−-salinity observed in different cotton cultivars. The results may provide new perspectives and valuable candidate gene resources for molecular breeding of chloride-salinity tolerance in cotton and other crops.

Primary charge separation in native and plant pheophytin a-modified reaction centers of Chloroflexus aurantiacus: Ultrafast transient absorption measurements at low temperature

Ultrafast transient absorption (TA) spectroscopy was used to study electron transfer (ET) at 100 K in native (as isolated) reaction centers (RCs) of the green filamentous photosynthetic bacterium Chloroflexus (Cfl.) aurantiacus. The rise and decay of the 1028 nm anion absorption band of the monomeric bacteriochlorophyll a molecule at the BA binding site were monitored as indicators of the formation and decay of the P+BA− state, respectively (P is the primary electron donor, a dimer of bacteriochlorophyll a molecules). Global analysis of the TA data indicated the presence of at least two populations of the P⁎ excited state, which decay by distinct means, forming the state P+HA− (HA is a photochemically active bacteriopheophytin a molecule). In one population (~65 %), P⁎ decays in ~2 ps with the formation of P+HA− via a short-lived P+BA− intermediate in a two-step ET process P⁎ → P+BA−→ P+HA−. In another population (~35 %), P⁎ decays in ~20 ps to form P+HA− via a superexchange mechanism without producing measurable amounts of P+BA−. Similar TA measurements performed on chemically modified RCs of Cfl. aurantiacus containing plant pheophytin a at the HA binding site also showed the presence of two P⁎ populations (~2 and ~20 ps), with P⁎ decaying through P+BA− only in the ~2 ps population. At 100 K, the quantum yield of primary charge separation in native RCs is determined to be close to unity. The results are discussed in terms of involving a one-step P⁎ → P+HA− superexchange process as an alternative highly efficient ET pathway in Cfl. aurantiacus RCs.

ВИКОРИСТАННЯ БІОЧАРУ І МІСКАНТУСУ ГІГАНТСЬКОГО (MISCANTHUS GIGANTEUS) ДЛЯ РЕМЕДІАЦІЇ ҐРУНТУ, ЗАБРУДНЕНОГО НАФТОПРОДУКТАМИ

The dynamics of changes in the chemical composition of soils contaminated with oil products during the vegetation of Miscanthus giganteus, as well as under the conditions of adding biochar (biochar) were studied. The possibility of using the culture of Miscanthus giant and biochar for soil remediation under conditions of oil pollution was analyzed. It was shown that the introduction of biochar into the soil enriched it with nitrate nitrogen, which was actively assimilated by giant miscanthus plants during the growing season. The absorption of nitrate anions by plants was especially active in the second series of the experiment, when the soil + biochar was contaminated with diesel fuel. It was established that the content of NH4+ ions in both series of the experiment increased until the end of the growing season. Obviously, ammonium nitrogen is absorbed to a lesser extent by M. giganteus plants, compared to nitrate. The increase in ammonium content can be additionally caused by the activity of soil microbes in the rhizosphere of plants, which contributes to the accumulation of ammonium nitrogen in the soil. It has been shown that miscanthus plants actively absorbed water-soluble forms of phosphorus, especially in the period from June to September. The application of biochar was a significant source of phosphorus, although its release into the soil is a rather slow process. It was determined that additional amounts of potassium were added to the soil with biochar, which was actively used by the M. giganteus culture. The minimum amounts of potassium in both series of studies were absorbed by plants of E groups, where the content of diesel fuel in the soil was the highest. The introduction of petroleum products had a minor effect on the value of exchangeable acidity. The addition of biochar contributed to the shift of the acid-base balance in the direction of alkalinity, but after the end of the miscanthus vegetation (September), a decrease in the pH of the saline extract of the soil was noted. It is shown that the most noticeable decrease in the concentration of diesel fuel in the soil was noted under the conditions of adding biochar and after growing miscanthus, which can be effectively used for the remediation of lands contaminated by oil products.

Kinetic and isotherm studies of Acid Orange 7 dye absorption using sulphonated mandarin biochar treated with TETA

This study contributes to the current state of knowledge by highlighting the physical–chemical interactions between biochar and dyes. The removal of Acid Orange 7 (AO7) dye by a modified biochar obtained from the wastes of mandarin peels (MPs) has been investigated in this work. A dehydration procedure with 80% H2SO4 under reflux was applied to produce an innovative biochar from MPs and then boiled with H2O2 and followed by boiling with triethylenetetramine to make mandarin biochar-C-TETA (MBCT). FTIR, SEM, EDX, BJH, BET, TGA, and DTA analyses were applied to investigate the MBCT. FTIR analysis showed an additional peak that confirmed the addition of the NH2 group to the MBCT structure. An amorphous carbon structure was also confirmed by XRD analysis. The AO7 dye solution pH was proved to give the best absorption at pH 2.0. Significant removal of AO7 dye 99.07% using an initial concentration of 100 mg/L of AO7 dye and a 0.75 g/L MBCT. The Langmuir (LNR) and Freundlich (FRH) isotherm models investigated the experimental results. The LNR was best suited to handle the working MBCT data. The maximum adsorption capacity (Qm) calculated for the MBCT was 312.5 mg/g using 0.25 g/L of the MBCT. Kinetic studies were conducted using the intraparticle diffusion (IND), film diffusion (FD), pseudo-first-order (PFOR), and pseudo-second-order (PSOR) models. The absorption rate was calculated using the ultimate value of the linear regression coefficient (R2 > 0.99), and the PSOR rate model was found to ideally describe the absorption process. The point of zero charge (pHPZC) was found to be 10.17. The electrostatic attractive-forces between the sorbent surface positively charged sites and negatively charged anionic dye molecules were the primary mechanism of the MBCT sorption of the AO7 dye’s anion absorption. The results indicate that the manufactured MBCT adsorbent may be useful for removing the AO7 dye from wastewater. MBCT can be used repeatedly for up to six cycles without dropping its absorption efficiency.

Stepwise deprotonation of truxene: structures, metal complexation, and charge-dependent optical properties.

As a planar subunit of C60-fullerene, truxene (C27H18) represents a highly symmetrical rigid hydrocarbon with strong blue emission. Herein, we used truxene as a model to investigate the chemical reactivity of a fullerene fragment with alkali metals. Monoanion, dianion, and trianion products with different alkali metal counterions were crystallized and fully characterized, revealing the core curvature dependence on charge and alkali metal coordination. Moreover, a 1proton nuclear magnetic resonance study coupled with computational analysis demonstrated that deprotonation of the aliphatic CH2 segments introduces aromaticity in the five-membered rings. Importantly, the UV-vis absorption and photoluminescence of truxenyl anions with different charges reveal intriguing charge-dependent optical properties, implying variation of the electronic structure based on the deprotonation process. An increase in aromaticity and π-conjugation yielded a red shift in the absorption and photoluminescent spectra; in particular, large Stokes shifts were observed in the truxenyl monoanion and dianion with high emission quantum yield and time of decay. Overall, stepwise deprotonation of truxene provides the first crystallographically characterized examples of truxenyl anions with three different charges and charge-dependent optical properties, pointing to their potential applications in carbon-based functional materials.

Multiconfigurational SCF and Short-Range DFT Combined with Polarizable Density Embedding: Comparison of Linear-Response and State-Specific Solvatochromic Shifts of Acrolein and Para-nitrophenolate in Water.

The polarizable density embedding model is combined with the multiconfigurational self-consistent field and MC-srDFT electronic structure methods to calculate solvatochromic shifts of the n-π* absorption of acrolein and the π-π* absorption of the para-nitrophenolate anion in aqueous solution. Differences between linear-response (LR) and state-specific (SS) solvent shifts are analyzed by assessing the contributions of different terms in the solvent potential. This comparison shows that the differences are not only due to the intrinsically different response of LR and SS excitation energies to the polarizability of the environment but also due to a different response to the static part of the environment potential. These observations show that even in nonpolarizable environments, LR and SS calculations based on SCF (orbital optimization) methods do not necessarily agree on the spectral shift. The difference can be as large as, or even dominate, the difference due to dynamical polarization.

Design of novel dual functional ionic liquids and DFT study on their CO2 absorption mechanism

Dual functional ionic liquids with the combinations of diethylenetriamine cation ([DETAH]+) or 1-ethanolamine-ethylenediamine cation([1-AOEt-EDAH]+) and 4-fluorobenzoate anion ([4-F-PhO]−) were explored for efficient CO2 capture in this work, and the absorption mechanisms of isolated ions and ion pairs were investigated using the dispersion corrected density functional theory (DFT) method. Above all, the possible reaction sites and reaction activity of TSILs were inferred by electrostatic potential (ESP) and Frontier molecular orbital analysis, then the reaction pathways for absorbing CO2 were proposed, and the transition state search of each elementary reaction by cation, anion and ion pair absorption was performed. Furthermore, the Gibbs free energy and reaction heat of each path were separately calculated, and the Gibbs free energy barrier and enthalpy barrier diagrams were drawn. In addition, the change of structural parameter, bond order and ADCH charge of reactants (R), transition states (TS), intermediates (IM), and products (P) were compared. The results showed that the absorption reaction of [DETAH]+ was the most likely to occur in kinetics, while that of [1-AOEt-EDAH]+ was favorable in thermodynamics. For the [DETAH][4-F-PhO], ion pair binding competed strongly with the CO2 chemisorption, while for [1-AOEt-EDAH][4-F-PhO], anions improved the stability of the whole structure, leading to the decrease of the Gibbs free energy barrier. Hopefully, the results of this work are helpful to provide a theoretical basis for designing of novel functional ionic liquids.

Low expression of bestrophin-2 is associated with poor prognosis in colon cancer.

The purpose of this research was to confirm the prognostic value of bestrophin-2 (BEST2), one of the hub genes in colon cancer, via bioinformatics analysis and validation in public databases and immunohistochemistry detection. The GEO2R online tool and Venn diagram software were utilized to identify differentially expressed genes (DEGs) from expression profiles, including GSE20916, GSE44861 and GSE74602, from the Gene Expression Omnibus (GEO). The overall survival (OS) and disease-free survival (DFS) of colon cancer patients from The Cancer Genome Atlas (TCGA) were analyzed through Kaplan-Meier survival curves. Verification of the significance of BEST2 in colon cancer was based on TCGA, Genotype Tissue Expression (GTEx) and 10 datasets from GEO. BEST2 expression was detected with immunohistochemistry (IHC) in 330 colon tissue samples on microarrays including 165 colon cancerand 165 adjacent normal tissues. For further validation, comprehensive analysis from tissue microarrays and multiple datasets was performed by the summarizing of receiver operating characteristic (SROC) curves and the standard mean differences (SMDs). BEST2 expression in various kinds of colon cancer tissues and cell lines in the context of pancancer was obtained from the Expression Atlas database. The CBioPortal database was queried to identify BEST2 gene alterations and mutation status in colon cancer. Correlated genes (CEGs) with BEST2 and DEGs from public database data were assembled for functional and pathway enrichment analysis. We identified 85 DEGs from the three datasets and screened out BEST2 as a prognostic predictor via the TCGA database. Colon cancer patients with high expression of BEST2 had better survival than patients with low BEST2 (HR=0.5, P=0.006) as shown in Kaplan-Meier survival curves in GEPIA. In all, 1463 colon cancer tissues and 1023 colon normal tissues were gathered via public databases as well as in-house tissue microarrays. The comprehensiveexpression analysis suggested low-expression of BEST2 in colon cancer (SMD=-2.48, 95% CI [-3.15- -1.80]) and the notable efficacy of BEST2 expression in differentiating colon cancer from noncancer samples (AUC=0.97). Gene alteration status of BEST2 occurred in 5% of colon cancer cases, mostly missense mutations and deep deletions. Genes positively correlated with BEST2 and DEGs primarily aggregated in pathways such as anion absorption, digestive juice secretion, cAMP signaling and so on (P<0.05). Ampleevidencesupportsthe role of BEST2 in distinguishing colon cancer from normal tissues in this research. Low expression of BEST2 is correlated with a shorter OS, which implies that BEST2 can be employed as a potential biomarker and therapeutictarget in colon cancer.

Ultrafast electron transfer at the interface of gold nanoparticles and methylene blue molecular adsorbates.

Due to their unique property of possessing localized surface plasmon resonance (LSPR), metal nanoparticles (MNPs) have drastically impacted many applications. For instance, local field enhancement through LSPRs and plasmonic hot electron transfer are known to enhance the efficiency of MNP-based photoreactions. Here, we report on the ultrafast electron transfer from gold nanoparticles (Au-NPs) to methylene blue (MB) molecular adsorbate using femtosecond pump-probe and steady-state absorption and emission spectroscopy techniques. Although the energy band alignment of the interface allows both dipole-dipole Förster resonance energy transfer (FRET) and charge transfer, because the MB emission intensity at the Au-NPs/MB nanocomposite decreased by a factor of ∼3.6, the FRET process was ruled out. Selective excitation of LSPRs at the Au-NPs/MB nanocomposite sample in pump-probe experiments led to the formation of the MB ground-state depletion and a positive induced absorption at wavelengths shorter than ∼500 nm, which was attributed to the shoulder of the MB- anion absorption. Furthermore, despite the fact that the concentration of Au-NPs in the nanocomposite sample is the same as that in the Au-NPs solution, the initial intensity of the LSPR depletion signal was about six times weaker than that in the Au-NPs sample. These observations suggest that electron transfer from excited Au-NPs to MB adsorbates took place on a time-scale that is shorter than the ∼50 fs experimental temporal resolution.

Substituent-dependent absorption and fluorescence properties of perylene bisimide radical anions and dianions.

Perylene-3,4:9,10-bis(dicarboximides) (PBIs) rank among the most important functional dyes and organic semiconductors, but only recently have their radical anions and dianions attracted interest for a variety of applications. Here, we systematically elucidate the functional properties (redox, absorption, and emission) of five PBI anions and dianions bearing different bay-substituents attached to the chromophore core. Cyclic voltammetry measurements reveal the influence of the substituents ranging from electron-withdrawing cyano to electron-donating phenoxy groups on the oxidation and reduction potentials that relate to the HOMO and LUMO levels ranging from -7.07 eV to -6.05 eV and -5.01 eV to -4.05 eV, respectively. Spectroelectrochemical studies reveal a significant number of intense absorption bands in the NIR-spectral range (750-1400 nm) for the radical anions, whereas the dianionic species are characterized by similar spectra to those for the neutral dyes, however being bathochromically shifted and with increased molar extinction coefficients of approximately 100 000 M-1 cm-1. The increase of the transition dipole moment is up to 56% and accompanied by an almost cyanine-like red-shifted (by 300 nm) absorption spectrum for the most electron-poor tetracyanotetrachloro PBI. Whilst the outstanding fluorescence properties of the neutral PBIs are lost for the radical anions, an appreciable near-infrared (NIR) fluorescence with a quantum yield of up to 18% is revealed for the dianions by utilizing a custom-built flow-cell spectroelectrochemistry setup. Time-dependent density functional theory calculations help to assign the absorption bands to the respective electronic transitions.

Excited-State Bond Contraction and Charge Migration in a Platinum Dimer Complex Characterized by X-ray and Optical Transient Absorption Spectroscopy.

Interactions between metal centers in dimeric transition metal complexes (TMCs) play important roles in their excited-state energetics and pathways and, thus, affect their photophysical properties relevant to their applications, for example, photoluminescent materials and photocatalysis. Here, we report electronic and nuclear structural dynamics studies of two photoexcited pyrazolate-bridged [Pt(ppy)(μ-R2pz)]2-type Pt(II) dimers (ppy = 2-phenylpyridine, μ-R2pz = 3,5-substituted pyrazolate): [Pt(ppy)(μ-H2pz)]2 (1) and [Pt(NDI-ppy)(μ-Ph2pz)]2 (2, NDI = 1,4,5,8-naphthalenediimide), both of which have distinct ground-state Pt-Pt distances. X-ray transient absorption (XTA) spectroscopy at the Pt LIII-edge revealed a new d-orbital vacancy due to the one-electron oxidation of the Pt centers in 1 and 2. However, while a transient Pt-Pt contraction was observed in 2, such an effect was completely absent in 1, demonstrating how the excited states of these complexes are determined by the overlap of the Pt (dz2) orbitals, which is tuned by the steric bulk of the pyrazolate R-groups in the 3- and 5-positions. In tandem with analysis of the Pt-Pt distance structural parameter, we observed photoinduced electron transfer in 2 featuring a covalently linked NDI acceptor on the ppy ligand. The formation and subsequent decay of the NDI radical anion absorption signals were detected upon photoexcitation using optical transient absorption spectroscopy. The NDI radical anion decayed on the same time scale, hundreds of picoseconds, as that of the d-orbital vacancy signal of the oxidized Pt-Pt core observed in the XTA measurements. The data indicated an ultrafast formation of the charge-separated state and subsequent charge recombination to the original Pt(II-II) species.

Skin absorption of mixed halide anions from concentrated aqueous solutions

Non-ideal behaviour of mixed ions is disclosed in skin absorption experiments of mixed halide anions in excised pig skin. Comparison of skin absorption of pure and mixed ions shows enhanced penetration of chaotropic ions from mixed solutions. An experimental design and statistical analysis using a Scheffé {3,2} simplex-lattice allows investigating the full ternary diagram of anion mixtures of fluoride, bromide and iodide. Synergism in mixed absorption is observed for chaotropic bromide and iodide anions. A refined analysis highlighting specific interactions is made by considering the ratio of the absorbed amount to the ion activity instead of the directly measured absorbed amount. Statistical analysis discards non-significant effects and discloses specific interactions. Such interactions between bromide and iodide cause an absorption enhancement of their partner by a factor of 2–3 with respect to the case of ideal mixing. It is proposed that enhanced absorption from mixed solution involves the formation of neutral complex species of mixed bromide and iodide with endogenous magnesium or calcium inside stratum corneum.

Temporary Anion Resonances of Pyrene: A 2D Photoelectron Imaging and Computational Study

The low-energy electron-scattering resonances of pyrene were characterized using experimental and computational methods. Experimentally, a two-dimensional photoelectron imaging of the pyrene anion was used to probe the dynamics of resonances over the first 4 eV of the continuum. Computationally, the energies and character of the anion states were determined using equation-of-motion coupled cluster calculations, while taking specific care to avoid the collapse onto discretized continuum levels, and an application of the pairing theorem. Our results are in good agreement with the predictions of electron-scattering calculations that include an offset and with the pyrene anion absorption spectrum in a glass matrix. Taken together, we offer an assignment of the first five electronic resonances of pyrene. Some of the population in the lowest-energy 2B1u resonance was observed to decay to the ground electronic state of the anion, while all other resonances decay by a direct autodetachment. The astronomical relevance of a ground-state electron capture proceeding via a low-energy resonance in pyrene is discussed.

Enhanced photocatalytic degradation of eco-toxic pharmaceutical waste diclofenac sodium by anion loaded Cu-Al LDH⋅Bi2O3 composites

BackgroundNowadays, the non-steroidal drug diclofenac sodium (DCF) has emerged as hazardous pollutant due to its eco-toxic nature and its efficient elimination from wastewater is emerging as crucial problem. But, low activity, high cost and instability of the conventional photocatalysts restrain their uses. MethodIn this study, different anion impreganted Cu-Al layered double hydroxides (LDH) and Bi2O3 derived heterocomposites have been examined as plausible photocatalysts for degradation of DCF under visible light radiation. These composites have synthesized by simple wet impregnation methods and characterized by several methods such as XRD, HR-TEM, XPS SEM-EDX, XPS, DRS, phototuminescence(PL), BET etc. Significant FindingsThe BET sorption isotherms indicate that the anion loaded composites are having larger specific surface area than the pristine one. Also, upon anion impregnation the zeta potential values shift towards more negative values confirming absorption of anions. They show significantly higher (65% for carbonate and 83% for sulphate) photcatalytic activity compare to the parent hybrid (53%). Here, the anions act as efficient electron scavengers to suppress the electron-hole pair recombination. The individual photocatalytic reactions follow pseudo-first order kinetics. Due to low cost, simpler preparation, enhanced activity and recyclability the anion loaded derivatives can emerge as excellent photocatalyst for eradicating DCF.